Place beets in a roasting pan and coat with olive oil and coarse salt and pepper. Roast in oven until fork tender, about 1 hour. Remove and let cool. Then remove the skin on each beet and cut into quarters.
Section the blood oranges, and and squeeze out remaining juice into a small bowl. Set orange slices aside. In bowl with juice, add sugar, mustard, olive oil and a pinch of salt and mix well for dressing.
Toss watercress and beets in dressing. Plate and add orange slices and goat cheese crumbs. Serve immediately.